cut a hole with boolean modifer not working
This is because the plane is non-manifold. It's a 2D object, which has no volume.
Either make it manifold by giving it volume (e.g. with a solidify modifier), or use the knife project tool instead of a boolean modifier:

Add a circle


⇧ Shift RMB on the plane so that both the circle and the plane are selected, and the plane is active (yellow outline).

Enter edit mode (↹ Tab), and align the view so that the circle outlines the hole you want to cut. In your case top view (Numpad 7) is probably good.

Press Knife project in 3D view &gt; tool shelf &gt; Tools &gt; Add:



Result: